Eyedrop test: There are many types of eyedrops and many types of eye drop tests.
One of the most common eye drop tests is pupil dilation. This examination enables your eye care professional to see more of your retina, the light-sensitive layer of tissue at the back of your eye.
Dilating (widening) the pupil permits the retina to be examined for signs of disease. To do this, drops are placed into the eye to dilate (widen) the pupil. After the examination, your vision may (or may not) remain blurred and bothered by the brightness of the sun for several hours.
The pupil, the opening of the iris, may appear to open (dilate) and close (constrict). The pupil determines how much light is let into the eye.
Dilation is the process of enlargement or expansion. The word "dilatation" means the same thing as dilation. Both come from the Latin "dilatare" meaning "to enlarge or expand."